Alarm apparatus



June27,1944- 'J.G. M. BRODEN 2,352,467

ALARM APPARATUS Filed Apiil 18, 1942 2 Sheets-Sheet l 14- y 12 Tag 2 Er 17 .25

June 27, 1944. V

J. G. BRODEN ALARM APPARATUS Filed April 18, 1942 2 Sheets-Sheet 2 7 Patented June 27, 1944 ALARM APPARATUS John Gustaf Mauritz Brodn, Malmo, Sweden 7 Application April 18, 1942, Serial No. 439,595 In Sweden March 18,. 1939 10 Claims. (Cl. 116-142) The invention relates to alarm apparatuses operated by air or gas under pressure and comprising an inlet channel for the pressure fluid, an outlet channel in the form of a sound member or funnel, and an oscillatable member, such as a tongue, diaphragm or the like member, which is adapted to close one end of both of said channels and to be actuated on oneside by the pressure fluid in the inlet and outlet channels and on the other side by the pressure in a closed chamber.

In hitherto known alarm apparatuses of the type referred to the said chamber is in open communication with the atmosphere so that the oscillating member is always under the influence of the substantially constant atmospheric pressure.

The oscillatable member is actuated by resonance from the outlet, that is from the funnel or soundmember, and, therefore, suifers from the inconvenience, that when the apparatus is operated with high effects, the sound wave in the funnel can be so strong and affect the oscillatable member to such .an extent, that the said member is liable to break.

The present invention has for its object to avoid this inconvenience. To this end, the oscillatable member around its periphery or a portion of the periphery or immediately near the periphery is fixed within a casing surrounding the alarm apparatus or abuts at the named place against a seat and is adapted to be actuated by mechanical forces directed against the seat and acting round the periphery or a portion of the periphery of said member, the pressure within said chamber being influenced by the pressure within said outlet channel through a passage provided with a counter-pressure valve or the like member.

The above-named passage preferably communicates with the narrowest inner cross-section of the sound member or funnel. The channels are advantageously provided in the walls of the chamber and funnel such as to communicate with each other, but said channels may be constituted by openings in the oscillating member or by a clearance within the periphery of the oscillating member and the wall of the chamber or by a recess at the edge of the oscillating member.

According to the simplest embodiment of the invention, the oscillating member itself consti tutes the counter-pressure valve in connection with the chamber. The oscillatable member may form one of the walls of the chamber, which wall by means of the pressure prevailing in the chamber is pressed towards a valve seat provided outside the chamber. In order to ensure effective abutment, resilient means may be provided for cooperating with the pressure of the fluid withinthe chamber. According to another embodiment, the oscillatable member may constitute'a seat for the back-pressure valve disposed within the chamber. In order to achieve supple abutment for the oscillatable member, the said member may be movable in the plane of the seat and in a direction at substantially right angles to said plane. bowl-formed diaphragm which is preferably provided with openings and the central portion of which abuts on a stationary portion in the chamber and the peripheral portion of which abuts.

against the oscillatable member. If the oscillatable member is constructed to constitute the counter-pressure valve, it may be provided with a flap resiliently mounted Withinthe chamber and maintained in abutment on the oscillatable member. Other means for realizing this purpose may be constituted by an elastic and substantially plane ring fixed within the chamber or by abowl-formed resilient member inserted between a Wall in the chamber and the oscillatable member and provided with an annular plane face directed towards the oscillatable member. a

As a result of the above-named arrangement, a portion of the pressure of the sound wave in the outlet, that is in the sound member or funnel, is always transmitted to the interior of the cham-- I ber, in which a pressure will be built up. This,

holds true especially if the connecting passage is provided with a counter-pressure valve.

be in a certain relationship to the pressure of the pressure wave, and, as a result thereof, the soundeffect can be increased to a much higher extent than previously without risk of break of the oscillatable member. A further advantage resulting from the pressure built up in the chamber consists in that the oscillatable member will be statically loaded on its rear side so that the said pressure Will be able to keep-the oscillatable member effectively pressed against the outlet and to close the outlet during that period of the course of the sound wave, when the wave causes a pressure below or slightly above the atmospheric pressure on that side of the oscillatable member which is directed towards the outlet.

A further advantage obtained by the invention consists in that due to the very loose fixing of the oscillatable member, the apparatus can be easily kept on the ground-note, even if oscillatable members with high specific tone are made use of.

The novel arrangement also offers the ad- Said resilient means may consist of it The pressure built up in the chamber will thus always vantage to save operating fluid, which will be more clearly apparent from the following description, and to be greatly independent of the pressure of the operating fluid, which pressure hitherto endangered the resistance of the oscillatable member.

In the annexed drawings, several embodiments of the invention are illustrated.

In Figs. 1 to 7 seven alarm apparatuses are illustrated in vertical sections. Fig.8 is a horizontal section of the embodiment shown in Fig. 7,

the section being taken on the line XX of Fig.

7, and Fig. 9 shows a pressure diagram for the operating fluid in connection with an alarm apparatus according to the invention.

In the several embodiments, similar reference numbers are used to denote similar parts.

The alarm apparatus shown in Fig. 1 includes a chamber I2, an oscillatable member I3, which usually consists of a diaphragm or tongue, and an outlet I4 in the form of a funnel or horn I5. According to Fig. l, the diaphragm is clamped between the wall I6 of the chamber I2 and the funnel I and abuts against the inlet to the funnel. A packing ll of metal or rubber is provided to supply the diaphragm at its fixed portion. A passage I8 connects the outlet I4 with the interior of the chamber I2, said connection being controlled by a counter-pressure valve I9. A passage 40 communicates the chamber I2 with the atmosphere. Operating fluid is supplied through a channel 20 and forces away the diaphragm so as to communicate with the outlet. The passage 2| is arranged to prevent fluid under presure from entering directly the chamber I2.

According to Fig. 2, the counter-pressure valve is formed by the diaphragm itself. To this end, the diaphragm freely abuts against a seat provided outside the chamber and is forced against said seat by means of a bowl-formed diaphragm 23 which is provided with openings 24. The passage between the outlet and the chamber is constituted by the clearance between the periphery of the diaphragm and the wall of the chamber, said passage being opened when the diaphragm is loaded by the fluid under pressure.

In the embodiments shown in Figs. 3, 4, 5 and 6, the .passage between the outlet and the chamber I2 is constituted by openings I8 in the diaphragm; In order to form counter-pressure valves, said openings I8 are adapted to cooperate accordingto Fig. 3 with an adjustable valve seat member 22, according to Fig. 4 with a flap 26 mounted on a leaf spring 25, according to Fig. 5 witha plane fixed ring- 21, and according to Fig. 6 with a resilient bowl-formed diaphragm 28 disposed in the chamber and provided with a plane annular flange.

In contrast to the embodiments described, the oscillatable member according to Figs. 7 and 8 is constituted by a tongue I3 fixed at one edge only in the wall of the chamber. In other respects, this embodiment is generally identical with the embodiments previously described.

If a signal is given, a standing sound wave is built up in the funnel, said sound wave being denoted by a sinecurve in Fig. 9. The ordinates represent pressures of the wave and the'abscissae represent time. The horizontal line denotes zero position. The wave is thus varying with respect to its pressure from a maximum value to a minimum value. When an air stream is supplied through the channel 20 into the outlet I4, this stream reaches its maximum pressure at the point 35 on the curve. This pressure results in that a certain quantity of air is forced into the chamber I2, the pressure in said chamber bein increased. At the point 36 on the curve, the pressure in the chamber will be great enough to close the connection via the diaphragm between the channel and the outlet I4. Meanwhile, the pressure in the outlet falls below atmospheric pressure, but is increased again due to the air flowing back, and at the point 31 on the curve fresh air can be forced from the channel 20 into the outlet, the pressure of said air then being increased up to the next maximum point 38 and is thereupon again reduced to the point 39. At this time, the diaphragm closes again the supply of air, and the course described above will be repeated. Air or other operating fluid will thus ,be consumed only during those periods when the pressure of the wave changes from the point 31 via 38 to the point 39. It follows therefrom that operating fluid will be saved by the arrangement according to the invention, since other arrangements of known construction are not able to keep the connection between the channel 20 and the outlet closed as long as the arrangement described but are opening and closing at considerably lower pressures. The arrangement described renders possible a certain equalization of the pressures prevailing on either side of the diaphragm and is thus, to a certain degree, independent of whether the pressure of the operating fluid is high or low, since it is only the pressure difference that is decisive for the stresses actuating the diaphragm.

In order to prevent high pressures from remaining in the chamber I2 after finished operation of the alarm apparatus, which pressures may render impossible anew subsequent operation of the apparatus, a narrow channel is preferably provided between the chamber I2 and the atmosphere. Said channel may be open or manually controlled. Such channel has no considerable influence upon the pressure in the chamber during the operation of the apparatus, provided that it has sufficiently small dimensions.

The invention is not limited to the embodiments described above, which are shown by way of example only. The invention may be embodied by other constructional modifications within the scope of the appended claims.

What I claim is:

1. An elastic fluid operated alarm apparatus comprising in combination, a casing, an inlet channel for fluid under pressure, an outlet channel forming a sound amplifying member, a closed chamber in said casing, an oscillatable member .arranged and constructed to close one end of both of said channels and to be actuated on one side by the fluid under pressure in said inlet and outlet channels and on the other side by the pressure prevailing, in said chamber, means for keeping at least part of the periphery of said oscillatable member by a peripherally arranged force, in abutment against said casing, a passage .connecting said chamber with said outlet channel, and a counter-pressure valve in said passage, said counter-pressure valve being arranged and constructed to permit part ,of said fluid to flowfrom said outlet channel to said chamber but preventing flow of fluid in the opposite direction.

2. An alarm apparatus as claimed in claim 1 and further characterized by said passage communicating with the narrowest inner cross-section of said outlet channel. Y

3. Analarm apparatus asclaime'd in claim 1 and further characterized by said passage being constituted by ducts provided in said casing and said sound amplifying member and communicating with each other.

4. An elastic fluid operated alarm apparatus comprising in combination, a casing, an inlet channel for fluid under pressure, an outlet channel forming a sound amplifying member, a closed chamber in said casing, an oscillatable member arranged and constructed to close one end of both of said channels and to be actuated on one side by the fluid under pressure in said inlet and outlet channels and on the other side by the pressure prevailing in said chamber, means for keeping at least part of the periphery of said oscillatable member by a peripherally arranged force in abutment against said casing, and means forming a clearance between the periphery of said oscillatable member and the wall of said chamber for connecting said chamber with said outlet channel.

5. An elastic fluid operated alarm apparatus comprising in combination, a casing, an inlet channel for fluid under pressure, an outlet channel forming a sound amplifying member, a closed chamber in said casing, an oscillatable member arranged and constructed to close one end of both of said channels and to be actuated On one side by the fluid under pressure in said inlet and outlet channels and on the other side by the pressure prevailing in said chamber, means for keeping at least part 01 the periphery of said oscillatable member by a peripherally arranged force in abutment against said casing, and a recess at the edge of said oscillatable member forming a connection between said chamber and said outlet channel.

6. An elastic fluid operated alarm apparatus comprising in combination, a casing, an inlet channel for fluid under pressure, an outlet channel forming a sound amplifying member, a closed chamber in said casing, an oscillatable member arranged and constructed to close one end of both of said channels and to be actuated on one side by the fluid under pressure in said inlet and outlet channels and on the other side by the pressure prevailing in said chamber, means for keeping at least part of the periphery of said oscillatable member by a peripherally arranged force in abutment against said casing, and a passage connecting said chamber with said outlet channel, said oscillatable member being arranged and constructed to form a counter-pressure valve in said passage, said counter-pressure valve being arranged to permit part of said fluid to flow from said outlet channel to said chamber but preventing flow of fluid in the opposite direction.

. both of said channels and to be actuated on one side by the fluid under pressure in said inlet and outlet channels and on the other side by the pressure prevailing in said chamber, peripherally actuating means for keeping the periphery of said oscillatable member in abutment against said casing, a passage connecting said chamber with said outlet channel, and a counter-pressure valve in said passage, said oscillatable member being constructed and arranged to' form a seat for said counter-pressure valve, said counter-pressure being arranged to permit part of said fluid to flow from said outlet channel to said chamber but preventing flow of fluid in the opposite direction.

8. An alarm apparatus as claimed in claim 1 and further characterized by an adjustaable seat for said counter-pressure valve.

9. An elastic fluid operated alarm apparatus comprising in combination, a casing, an inlet channel for fluid under pressure, an outlet channel forming a sound amplifying member, a closed chamber in said casing, an oscillatable member arranged and constructed to close one end of both of said channels and to be actuated on one side by the fluid under pressure in said inlet and outlet channels and on the other side by the pressure prevailing in said .chamber, means for keeping at least part of the periphery of said oscillatable member in abutment against said casing, a passage connecting said chamber with said outlet channel, a counter-pressure valve in said passage, and a second passage adjacent the diaphragm on the side opposite said chamber for preventing fluid under pressure from entering the chamber.

10.-An elastic fluid operated alarm apparatus comprising in combination, a casing, an inlet channel for fluid under pressure, an outlet channel forming a sound amplifying member, a closed chamber in said casing, an oscillatable member constructed and arranged to close one end of both of said channels and to be actuated On one side by the fluid under'pressure in said inlet and outlet channels and on the other side by the pressure prevailing in said chamber, a peripheral abutment for said oscillatable member outside said chamber, and resilient means in said chamber actuating at the periphery of said oscillatable member for keeping said oscillatable member in contact with said abutment.

JOHN GUSTAF MAURITZ BRODEN, 

